Hours of Prayer & the Heavens

So to be clear for visitors and for these calculations, this location applies only to one specific job: determining which month begins the New Biblical Year. It is not used for ordinary month-to-month New-Moon calculations - the starting date of any given month is still computed from the location the user selects on this page. For the New Year determination specifically, two reference points are used on purpose, each for a different part of that determination. First, a sighting point west of Jerusalem (Tel Kesalon, detailed below) is used to determine which day is the New Moon day for the candidate first month - we pick a qualifying location farther west because its slightly later sunset gives the young crescent marginally greater elongation and therefore slightly better visibility, letting us accept the earliest day the crescent could legitimately have been sighted and reported back to Jerusalem by Biblical Midnight to begin that month. Second, the Temple Mount in Jerusalem is used for the equinox test: once that New Moon day is set, we evaluate whether the equinox has occurred by the end-of-the-14th sunset measured at the Temple Mount. So for the New Year question, the western point decides which day the candidate month starts, and the Temple Mount decides the equinox cutoff at the end of the 14th. Here is the information about that western sighting point used for the New Year determination:

Tel Kesalon (also spelled Tel Ksalon) is the archaeological mound identified with the Biblical town of Chesalon (Hebrew כְּסָלוֹן, transliterated Kesalown from the Leningrad Codex spelling; rendered "Chesalon" in the King James Version via the Greek/Latin; appearing as Chasalon in Eusebius of Caesarea's 4th-century Onomasticon), and it is the location the default calculation should use as the New-Moon sighting point for determining which day is New Moon day for the candidate first month of the Biblical New Year; its precise coordinates are 31.781111° N, 35.051111° E (Palestine 1928 Grid 154927/132050), OpenBible geocoding id mb905e4. The mound sits on the shoulder of Mount Jearim (Hebrew הַר יְעָרִים, Har Ye'ariym, KJV "mount Jearim"), meaning "Mountain of Forests," a ridge linguistically related to the neighboring town of Kiriath-jearim (Hebrew קִרְיַת יְעָרִים, Qiryat Ye'ariym, KJV Kirjath-jearim, "City of Forests"); to be clear about one distinction worth preserving in any display, Chesalon is the town and mound, which is the precise point the default calculation should use, whereas Mount Jearim is the broader ridge on which the town sat, so the coordinate pins the town. The modern Israeli moshav Ksalon/Kesalon is a separate nearby locality with its own coordinate of approximately 31.77389° N, 35.04944° E (about 0.5 km south of the mound), and it is not the point used for these calculations. The default calculation should use a location west of Jerusalem for the sighting point deliberately: because a more westerly location experiences a marginally later sunset, the young crescent attains slightly greater elongation from the sun and therefore slightly improved visibility, and choosing such a point lets the calculation recognize the earliest day on which the New Moon could legitimately have been seen and reported to Jerusalem in time to begin the month. The point should not simply be the westernmost possible spot, though - it should be the westernmost one consistent with a timely report, because from Tel Kesalon, roughly 15 km west of Jerusalem, a witness traveling by donkey could carry the testimony to Jerusalem by Biblical Midnight (the midpoint between sunset and sunrise) following the sighting, whereas a substantially more westerly point could not be reached within that interval. It also helps that the terrain descends westward into the Sorek Valley, giving a lower and more open western horizon, where the crescent would be sought shortly after sunset, than Jerusalem itself, whose western side is partly blocked by higher hills. It bears repeating that this western point governs only one function, namely determining which day the candidate first month begins; the separate equinox test (whether the equinox has occurred by the sunset concluding the fourteenth day) is evaluated at the Temple Mount in Jerusalem, not at this location, and this Tel Kesalon location is used only for the New Year determination and not for ordinary month-to-month New Moon reckoning, which continues to use the location selected by the user. The Biblical anchor for the identification is Joshua 15:10, which traces the northern border of Judah "...along unto the side of mount Jearim, which is Chesalon, on the north side, and went down to Beth-Shemesh, and passed on to Timnah"; the coordinate is the consensus point aggregated by OpenBible.info from standard references (Anchor Yale Bible Dictionary 1992; Eerdmans Dictionary of the Bible 2000; HarperCollins Concise Atlas of the Bible 1991; Zondervan Atlas of the Bible 2010; Zondervan Illustrated Bible Backgrounds Commentary 2009; Wikidata Q6374592; Amud Anan survey database), documented at https://www.openbible.info/geo/modern/mb905e4/kesla and https://www.biblewalks.com/kesalon/, with Hebrew vocalization drawn from the Leningrad Codex text at https://tanach.us. Regarding "medium confidence": This refers to how sure we can be that this specific hill is the same place the Bible calls Chesalon in Joshua 15:10. Three things point to that conclusion, including 1) the old Arabic village name "Kesla" still resembling the ancient name "Chesalon", 2) the site fitting the border description in Joshua 15:10, and 3) people have surveyed the hill and found broken pottery and remains of a settlement going back ~3,000+ years - but no actual "inscription" has been found (that I know of) at the site to say for certain.